scsi: cxlflash: Hardware AFU for OCXL

When an adapter is initialized, transport specific configuration and MMIO
mapping details need to be saved. For CXL, this data is managed by the
underlying kernel module. To maintain a separation between the cxlflash core
and underlying transports, introduce a new structure to store data specific to
the OCXL AFU.

Initially only the pointers to underlying PCI and generic devices are added to
this new structure - it will be expanded further in future commits. Services
to create and destroy this hardware AFU are added and integrated in the probe
and exit paths of the driver.

Signed-off-by: Uma Krishnan <ukrishn@linux.vnet.ibm.com>
Acked-by: Matthew R. Ochs <mrochs@linux.vnet.ibm.com>
Reviewed-by: Andrew Donnellan <andrew.donnellan@au1.ibm.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>